Hygroscope.



No. 798,938. PATBNTED SEPT. 5, 1905. H. E. WETHERILL.

HYGROSCOPE.

APPLICATION FILED JULY 18,1904.

INYENTDH WITNESSES UNITED STATES PATENT QFEIGE.

HYGROSCOPE.

Specification of Letters Patent.

Patented. Sept. 5, 1905.

Application filed July 18, 1904. Serial No. 217,021.

To (all wit/mt it nmy concern.-

Be it known that I, HENRY EMERSON \Vu'rir- ERILL, a citizen of theUnited States, residing in the city of Philadelphia, State ofPennsylvania, have invented certain new and useful Improvements inHygroscopes, of which the following is a full, clear, and exactdescription, reference being had to the accompanying drawings, forming apart of this specification.

My invention relates to hygroscopes, and has for its object to provide areliable instrument of that class which while capable of use in generalmeteorological work is adapted especially for measuring the perspirationin pathologic diagnosis. Hereto'forc no such instrument has been at theservice of the medical profession except one or two, which are expensiveto construct, easily broken or operatively disrupted, and not capable ofaccurate adjustment nor adapted to use under many conditions whichcommonly prevail in the laboratory, especially in pathologic diagnosis.

My invention has for its object to provide an instrument of this classnot open to these objections which shall be durable, simple, compact,cheap in construction, readily adjustable, perfectly air-tight underproper application, and reliable in its measurements of moisture.

To these ends it consists of the device hereinafter described, the novelfeatures in which will be pointed out in the several clauses of claim.

In the drawings illustrating my invention, Figure I is a plan view ofthe dial-plate, showing no other part of the instrument except the endof the spring-post which projects through the dial and the washer, towhich said end is riveted. Fig. 2 is a bottom plan View of the devicewith the perforated bottom plate removed. Fig. 3 is a vertical sectionon line I 2 of Fig. 2 looking to the left. Fig. t is a plan view of theperforated bottom plate. Fig. is a side elevation intended to illustratethe construction and arrangement of certain elemental features, and Fig.6 is a side elevation of the indicator.

The shell or casing A is of stiff metal and light in weight, and forthese purposes I make it of aluminium, and this metal is desirable, asit avoids condensation of moisture, which would affect the degrees ofhumidity measured. Its vertical wall a is preferably annular in shape,and at each head end it is provided with an internal shoulder b 7),slightly beveled,

the function thereof being to removably hold the correspondingly-shapedannular edge of the dial-plate and of the perforated bottom plate, bothhereinafter described.

The dial-plate contains upon its top or outer surface the numerals 25,50, 75, or others,

indicating relative humidity percentages of moisture, and on its underor inner surface the dial-plate contains the index-line 0. (Shown inFig. 1 in dotted lines.) For purposes of lightness and durability and tolessen the amount of moisture deposit on the dial I have substituted forglass a thin and transparent celluloid as the material for thedial-plate as being preferable. Mica, glass, gelatin, or othertransparent or translucent material can be used, but with lessadvantage.

The indicator-finger (7 (shown in detached elevation in Fig. 6) mustnecessarily be of the lightest possible weight, and for this reason,while preserving stiffness, I make it of aluminium. It consists of athin rod bent downward at its inner end to form the side (1, then upwardto form the side d, the purpose being to f0 rm a loop (5. A third bond1! is preferably added to better preserve the stiffness of theloop-walls. An arrow 01' perforated point may be used, the width of thepoint being one-lifth the distance between the smallest graduations ofthe scale.

The sensitive spring is made spiral in form. It is a thin copper bandcovered on the outer side with a thin membrane fastened to the surfaceof the metal by cement, such as rubber-cement. The copper may be platedor dipped in a lacquer to protect it from corrosion. I have discoveredby a series of experiments that the skin of an cgg-namely, the membranenext to the shell and that surrounds the albumen-is exceedinglydesirable for that purpose, though paper, gelatin, the knownphoto-negative films, or human hair freed from fat may be substituted,but with less advantage. The membrane or its said substitutes in orderto make it more highly sensitive to moisture must be treated with achemical solution. but chiefly to make it contract under the slightestmoisture, I prepare the membrane by submitting it to a coating ofchlorid of cobalt, for which purpose a four-tenths saturated aqueoussolution is best, as found by extensive testing. Herein lies a basicprinciple of my invention namely, in the provision of ahygroscopicmembrane chemically treated with a hygroscopic salt; but the As apreservative of it, 7

mounting of such a membrane upon a metallic band carrying theindicator-point is equally fundamental, and so, also, is the provisionof such a band in the form of a spiral or so that the change of size ofthe membrane will cause the copper spring to move radially.

The metallic support for the chemicallytreated membrane is preferablymade for a medical hygroscope of a thin spri-ngy copper bandtwo-thousandths of an inch in thickness and three sixteenths of an inchin width,- though silver metal would answer or gold alloy. The band isto be spiraled. Each end is preferably given a short bend to bind themembrane thereon, and is preferably pointed or narrowed at the inner endfor easy insertion in the supporting-post hereinafter described. It isspiraled enough to give two and one-half turns or rounds when theindicator shows seventy-five per cent. of humidity and is so spiraledand arranged in the post that the final or outward turn or bend of themetal band will impart a circular plane of movement to the indicatorcarried thereby, centering on the supporting-post as its axis in orderthat it shall always rotate in a true circular path. The first turn ofthe spiral must also be a circular curve.

The indicator is mounted on the spiral metal band by slipping its loopoverthe outward end of the metal band, and obviously this constructionand arrangement of the parts will provide for the general adjustabilityof the indicator on its spiral metallic carrier, a new and importantfactor of great value. The indicator clamps firmly in its place on itscarrier withoutthe use of cement, which is a decided improvement. I

The supporting-post m is substantially a cylinder of metal with reducedshouldered ends at either or both extremities. The upper end is suppliedwith a lower washer a, and its projecting end above the washer passesthrough an aperture in the dial-plate, and another washer n is placedthereon above the dial-plate, the top being thenriveted on the upperwasher. The extreme top end of the post is slotted, as at 01 Fig. 1, sothat the post, indicator, and its spiral carrier can be moved rotatablyas a whole for the purpose of final adjustment. The body portion of thepost is slotted longitudinally, as at t, as it is within this slot thatthe inner end of the spiral metal band is inserted and thereby mounted;but the slot is made slightly longer than the width of the band in orderthat it may be adjusted vertically on the post.

The instrument can be and frequently is with. advantage used with anopen base; but I prefer to provide a basal covering in the form of theannular plate T. (Shown in Fig. f.) This plate is of light aluminiummetal, with an edge adapted to fit the inner shoulder on the edge of thecasing or shell. It is perforated in several places, as at p, in theregion of the spiral spring to admit cutaneous moisture in the form ofvapor from the body when placed upon a patient. The basal plate willprevent hairs from stopping the motion of the spiral carrier.

The smaller perforation s is provided to admit the passage therein ofthe lower end of the post, thereby not only holding the parts together,but bringing the apertures 9 immediately below the sensitive spiral bandcarrying theindicator. To remove the closing-cap and open the casing, itis merely necessary to lightly press the head of the supporting-post.

The operation of the device is obvious from the description given, andit is sufi'icient to note that the fundamental principle in the mode ofoperation of the indicator-carrier is the spiral form of the sensitivecarrier, which being covered with a chemically-sensitized membranecontracting under the effect of moisture or expanding under the loss ofsuch moisture absorbed causes the balanced indicator to rotate radially.The changes of color which take place in the chemically-treated membranemay be used to standardize the instrument in comparison with achlorid-of-cobalt color-scale.

Some of the decided advantages of my device from a mechanical standpointare that it is simple in construction, of few parts, and most of itselements replaceable without affecting the others. From a medical pointof View it is easily cleaned, can be made antiseptic, its form andcharacter are such that it can be applied to the skin or in other waysto a patient, so as to exclude all atmospheric humity, and after use itsperforated plate can be removed and the casing inverted, so that themoisture inside the instrument will pass off and the elements restoredto mark the normal humidity of the outside atmosphere. The markings ofthe indicator in clinical diagnosis can be plotted on charts similar tothose used in the wards of hospitals, and as the determination of theamount of perspira-' tion in different conditions is of considerablediagnostic, therapeutic, and prognostic value it is important to have aninstrument that will mathematically express the condition, and thus aidin symptomatology and secondarily in treatment. With my instrumentproperly applied, as aforesaid, to the skin of a patient the indicatorwill in a few minutes enable a correct reading of the percentage ofmoisture to be made.

Having thus described my invention, I claim 1 as new and desire tosecure by Letters Paten t 1. In a hygroscope, a hollow supportingframe,a transparent dial-plate thereon, a post mounted in said dial-plate andextending within the frame, a spiral metallic band lined on one sidewith a contractible material which has been made sensitive to moisture,said spiral band being arranged edgewise within the frame and mounted byone end in said post,

and an indicator carried on the free end of said band, operating to moveradially on the surface of the dial-plate.

2. In a hygroscope, the combination with a suitable containing-casingprovided with a graduated dial-plate, of a post supported witln in thecasing, an indicator-carrier mounted edgewise and by one of its ends insaid post, said carrier eonsistingojf a flatspiral band havingaplurality of true circular curves whereby its free end may rotate in thea re of a true circle, said carrier-baml being made sensitive tomoisture, and an indicator-linger mounted on the free end of the spiralcarrier.

3. In a hygroscope com prising a hollow containing-easing, cylindricalin shape, a transparent dial-plate closing one end thereof, animlicator-carrier post, means to support one end of said post rotatablyin said dial-plate, a spiral band of metal, a coveringon said band,which is made sensitive to moisture, an indicator-finger mounted on thefree end of said band, and a removable plate forming the bottom of thecasing and provided with an opening to receive the lower end of the postwhen the instrument is closed.

a. In a hygroscope, an indicator-carrierconsisting of a spiraled band,means supporting it at one end, in such manner that its free end willmove radially under a longitudinally-exerted force, and a liningcemented to one side thereof, said lining consisting of the skin of anegg which has been coated with chlorid of cobalt.

5. In a hygroscope, a containing-casing, a transparent dial-platethereon, a longitudinally-slotted post supported within the easing, aspiral indicator-carrier covered with a sensitive membrane, andhavingoneof its ends mounted vertically adjustable in the slotted post,and an indicator carried on the free end of the spiral carrier.

6. In a hygroscope, the combination with a suitable casing and asensitized spiral indicator-carrier mounted therein, of an indicator therear end of which is provided with a loop whereby it may be supportedadjustably on the indicater-carrier.

7. In a hygroscope, a longitudinally-slotted post, a spiral band, madeeontractible under moisture and having its inner end mounted verticallyadjustable in said post, and an indicator-linger having a looped endmounted longitudinally adjustable on the free end of the spiral band.

8. In a hygroscope, a containing-easing. a transparent dial-platethereon, a post maintained by one end in the dial-plate, a removableperforated base-plate for the casing, an opening in said plate toreceive the lower end of the post, and a sensitized spiralindicatorcarrier mounted by one end in said post.

9. In a hygroscope, a hollow casing interiorly shouldered at one end, aperforated plate adapted to be removably held in the shouldered end ofthe casing, atransparent dial sup ported in the opposite end of thecasing, a post supported within said casing, a spiral band lined with acontractible material made sensi tive to moisture and mounted edgewiseby one end in said post; and an indicator-linger mounted on the 'freeend of said spiral band.

In testimony whereof I have hereunto aflixed my signature this 12th dayof July, A. I). 190%.

HEXR Y EMERSON \YE'IHERI [IL- "itnesses:

IIIGNRY T. GULLMANN, H. .l. FENTON.

